Known in the art is a crystal vibration element comprised of an AT cut blank of crystal on the two major surfaces (the widest surfaces (the front and back) of a plate shaped member) of which a pair of excitation electrodes are provided (for example Patent Literature 1). Such a crystal vibration element has a pair of extraction electrodes for mounting this crystal vibration element on an element mount member. A pair of extraction electrodes for example has a pair of pad parts at the end parts of the crystal blank in the longitudinal direction. Further, by an arrangement of the pad parts so as to face the pads of the element mount member and joining of the two by bumps (made of for example a conductive adhesive), the crystal vibration element is supported in a cantilever fashion. As a result, the crystal vibration element can vibrate in most of its length except the end parts in the longitudinal direction.
Further, as the crystal vibration element described above, there is also known a so-called mesa-structure (for example Patent Literature 1). In a mesa type crystal vibration element, the crystal blank has a mesa part provided with a pair of excitation electrodes and has an outer circumferential part which is positioned at the periphery of the mesa part and is thinner than the mesa part. The pad parts of the pair of extraction electrodes are provided in the outer circumferential part. In a mesa type crystal vibration element, it is easy to enclose energy in the mesa part. Therefore, for example, the influence of the joints of the extraction electrodes upon the vibration characteristics is reduced.
Patent Literature 1 proposes that the length Sx (mm) of the pad parts in the longitudinal direction of the crystal vibration element be made smaller than dx−0.05 where the distance from the outer edge of the outer circumferential part to the outer edge of the mesa part (inner edge of the outer circumferential part) is dx (mm). Although the proposal relates to the size of the pad part the proposal suggests to make the distance between a pad part and the mesa part 50 μm or more.